Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
  • H01M8/184—Regeneration by electrochemical means
  • H01M8/186—Regeneration by electrochemical means by electrolytic decomposition of the electrolytic solution or the formed water product
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
  • C07C1/02—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon
  • C07C1/10—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with water vapour
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/02—Hydrogen or oxygen
  • C25B1/04—Hydrogen or oxygen by electrolysis of water
  • C25B1/042—Hydrogen or oxygen by electrolysis of water by electrolysis of steam
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
  • H01M8/04014—Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
  • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
  • H01M8/04097—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with recycling of the reactants
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
  • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
  • H01M8/04119—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
  • H01M8/04156—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying with product water removal
  • H01M8/04164—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying with product water removal by condensers, gas-liquid separators or filters
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
  • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
  • H01M8/0432—Temperature; Ambient temperature
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
  • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
  • H01M8/0438—Pressure; Ambient pressure; Flow
  • H01M8/04388—Pressure; Ambient pressure; Flow of anode reactants at the inlet or inside the fuel cell
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
  • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
  • H01M8/04791—Concentration; Density
  • H01M8/04798—Concentration; Density of fuel cell reactants
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
  • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
  • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
  • H01M8/0618—Reforming processes, e.g. autothermal, partial oxidation or steam reforming
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
  • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
  • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
  • H01M8/0625—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material in a modular combined reactor/fuel cell structure
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
  • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
  • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
  • H01M8/0637—Direct internal reforming at the anode of the fuel cell
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
  • H01M8/0662—Treatment of gaseous reactants or gaseous residues, e.g. cleaning
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
  • H01M2008/1293—Fuel cells with solid oxide electrolytes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2250/00—Fuel cells for particular applications; Specific features of fuel cell system
  • H01M2250/40—Combination of fuel cells with other energy production systems
  • H01M2250/402—Combination of fuel cell with other electric generators
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• the present invention relates to a fuel cell system having an increased total efficiency and a method for operating the fuel cell system with increased total efficiency.
• Fuel cell systems especially high temperature fuel cell systems (e.g. SOFC) with an operation temperature of around 600-800 °C, are widely used in the prior art for generating electric power produced by the redox reaction of a fuel stream and an oxidant stream.
• SOFC high temperature fuel cell systems
• hydrogen is preferably hydrogen as the fuel gas since it does not include carbon-containing substances, which can lead to carbon deposition inside the fuel cells.
• fuel cell systems known in the prior art typically have a maximum fuel utilization of about 70 to 80 % only, these fuel cell systems showing a low total efficiency and generate up to 60 % waste heat. Due to the heat produced by the electrochemical reaction inside the fuel cell, cooling needs to be carried out. This is typically done by using the air supplied to the cathode for this purpose, which consumes a lot of energy for the air blower.
• the inventive fuel cell system is arranged for the conversion of pure hydrogen fed to the (reversible) fuel cell system and comprises at least one fuel cell, which, according to a preferred embodiment, is a solid oxide fuel cell (SOFC).
• the fuel cell itself comprises an anode, a cathode and an electrolyte, which is provided between the anode and cathode.
• the fuel cell is further arranged for an internal reformation of methane. “Internal” in this sense means “within the fuel cell”.
• a reformation section forms part of the fuel cell and is thus, provided within the fuel cell (inside of the fuel cell), and is particularly located near and/or at the electrochemical reaction zone of the fuel cell and therefore in direct thermal contact with the fuel cell reaction zone.
• Fuel is supplied to an anode inlet of the anode via a fuel conduit and the fuel introduced into the fuel conduit via a fuel conduit inlet is pure hydrogen (which, of course, depending on its origin may contain unavoidable impurities up to 5 Vol.-%).
• An anode exhaust conduit is provided, which connects an anode outlet of the fuel cell and a methanation unit.
• the methanation unit is capable of producing methane from anode exhaust. More particular, the anode exhaust contains hydrogen and carbon containing substances, and therefore, the methanation unit can produce CH 4 out of a mixture containing CO, CO 2 and hydrogen.
• the methanation unit further comprises a methanation unit exit, and a methanation unit exhaust conduit connects the methanation unit exit and the fuel conduit.
• the methanation unit exhaust conduit is coupled to the fuel conduit so that methane produced in the methanation unit is supplied to the fuel conduit and mixed with the pure hydrogen supplied to the fuel conduit via the fuel conduit inlet.
• this methane once fed to the fuel cell system, is not supplied from the outside so that methane is consumed by operating the fuel cell system, but instead the methane used for the reformation is generated in the methanation unit, which is one of the essential components of the fuel cell system.
• the amount of methane produced in the methanation unit is controlled such that it is equal to the amount of methane reformed internally inside the fuel cell so that the content of methane cycling through the fuel cell system is constant. This results in a closed methane cycle.
• the respective amount of reformed methane can be adjusted so that no or only a minimum of cooling energy has to be supplied to the fuel cell via e.g. the cathode.
• the fuel cell system further comprises a water removal and/or water condenser unit coupled to the methanation unit exhaust conduit, which may be provided downstream to a first heat transferring means, if present.
• the water removal and/or water condenser unit is capable of reducing the steam content of the methanation product so that the fuel mixture fed to the fuel cell only contains a small amount of residual steam. High amounts of steam in the fuel mixture greatly reduce the electrochemical efficiency of the fuel cell reaction by reducing the Nernst voltage potential.
• the fuel cell of the inventive fuel cell system further comprises an oxidant conduit for supplying oxidant, like oxygen or air, to the cathode via a cathode inlet. Further provided is an oxidant exhaust conduit.
• the above-described fuel cell system further preferably comprises means to control the ratio of hydrogen to methane in the fuel mixture depending to the fuel cell operating temperature and pressure, such that carbon deposition is thermodynamically prevented without the necessity of presence of water steam in the fuel mixture, i.e. without adding water to the fuel supplied to the fuel cell, wherein the means are capable of adjusting the ratio according to the following values and intermediate values by linear interpolation between the values given:
• the methanation unit exhaust conduit comprises first heat transferring means (like e.g. a heat exchanger) for transferring heat from methanation unit exhaust to the fuel (mixture) supplied to the anode inlet. Since the methanation reaction is an exothermic reaction, transferring heat contained in the methanation product to the fuel in the fuel conduit increases the heat utilization rate and thus, contributes to the overall increase of the total degree of efficiency.
• first heat transferring means like e.g. a heat exchanger
• the fuel cell system advantageously further comprises a steam circuit, capable of producing electric power using water vapor.
• the steam circuit is thermally coupled to the methanation unit, in so far as the methanation unit reaction zone, where the exothermic methanation occurs, is directly or indirectly arranged for transferring heat to the steam circuit, preferably to the evaporation section of the steam circuit. Using this transferred heat, water vapor can be produced easily, which then can be used to drive a turbine or the like, which then produces electric power.
• the steam circuit preferably comprises at least one turbine.
• the anode exhaust conduit between the anode outlet and the methanation unit of the fuel cell system may further comprise second heat transferring means (like e.g. a heat exchanger) for transferring heat from the anode exhaust to the fuel or fuel mixture to be supplied to the anode via the fuel conduit.
• second heat transferring means like e.g. a heat exchanger
• the carbon related emissions can be kept at a minimum, comprising only of minor gasket leakages.
• the total efficiency degree of the inventive fuel cell system can be further improved according to an embodiment, in which the content of methane cycling through the fuel cell system is set such that at least 30%, preferably at least 50% and more preferably at least 70% of the heat of the fuel cell reaction is consumed by the reformation reaction.
• the fuel cell is a reversible fuel cell and can be operated in a fuel cell mode and additionally an electrolysis mode.
• the fuel cell is preferably capable of converting a mixture of hydrogen and water steam into a mixture richer in hydrogen without the presence of carbon containing gases. This effectively enables the production of pure hydrogen in the system, which, after condensation of residual water steam, can be provided to external hydrogen users or stored to be re-utilized in the fuel cell operating mode.
• a further aspect of the present invention relates to a method of operating the above-described fuel cell system. Accordingly, in view of the components and functionality of the fuel cell system, additional reference is made to the annotations and explanations provided above.
• the method comprises feeding pure hydrogen into the fuel conduit inlet of the fuel conduit.
• the hydrogen serves as the only fuel to be converted in the overall balance of the fuel cell system so that there are overall no carbon dioxide emissions from the system.
• the pure hydrogen is mixed with methanation unit exhaust fed from the methanation unit exhaust conduit, after water has been removed or condensed from the methanation unit exhaust.
• Said methanation unit exhaust comprises hydrogen and methane as the main components.
• the obtained mixture is fed to the anode inlet.
• methane contained in the mixture is then reformed with water steam primarily originating from the electrochemical oxidation of hydrogen inside of the fuel cell so that hydrogen and carbon oxides are produced in an endothermic reformation reaction.
• a fuel cell reaction is carried out in the fuel cell, wherein hydrogen serves as the primary fuel, which is converted.
• Anode exhaust exiting the anode outlet is then supplied to the methanation unit via the anode exhaust conduit and methane is generated out of the anode exhaust in the methanation unit.
• the amount of methane produced in the methanation unit is equal to the amount of methane reformed in the internal reforming so that the content of methane cycling through the fuel cell system is constant and a closed methane cycle is provided.
• the methane used in the above operating method is kept at a constant amount and no new methane is fed via the fuel conduit, carbon dioxide emissions of the fuel cell system can be prevented efficiently. Furthermore, since methane is reformed within the fuel cell, heat produced by the fuel cell reaction can be used for carrying out the endothermal reformation reaction so that the fuel cell is directly cooled by the internal reformation reaction. Therefore, cooling mainly by distributing high amounts of air to the cathode, which consumes a lot of electric power for e.g. a fan or the like, can be avoided. Accordingly, heat generated in the fuel cell system is effectively used and not wasted, which increases the total efficiency degree of the fuel cell system.
• the operating conditions of the fuel cell are controlled by adjusting the ratio of cycling hydrogen and methane depending on operating pressure and temperature inside the fuel cells as follows, such that carbon deposition is thermodynamically not favored even when no water vapor is present, whereby linear interpolation between the given values provides exemplarily an approximate borderline for carbon deposition, which must not be undercut: • atmospheric pressure, 550°C, volume ratio H 2 :CH 4 > 1.7; or
• the method comprises transferring heat from methanation unit exhaust to the mixture to be fed to the anode inlet. This improves the thermal efficiency of the fuel cell system.
• the method may comprise a step of transferring heat from the methanation unit to a steam circuit to support the production of electric power using water vapor in the steam circuit.
• the electric power production can be increased directly.
• a turbine may be driven by water vapor produced by heating water with heat generated during the methanation reaction.
• the removing of water or the condensing of water is preferably carried out after transferring heat from methanation unit exhaust to the mixture to be fed to the anode inlet, wherein in particular, the removing of water or the condensing of water is controlled such that a content of water vapor in the mixture at the anode inlet is less than 10 Vol%, preferably less than 3 Vol%, relative to the total volume flow of the mixture supplied to the anode inlet. This guarantees a high efficiency and power generation.
• the content of methane cycling through the fuel cell system is set such that at least 30%, preferably at least 50% and more preferably at least 70% of the heat of the fuel cell reaction is consumed by the reformation reaction.
• the method may further comprise a step of cycling an additional amount of hydrogen through the fuel cell system, wherein the cycling additional amount of hydrogen is not consumed.
• the fuel cell system may comprise more than one fuel cell and the sum of the current flowing through all individual fuel cells (current density times the total cell area in the plurality of fuel cells in the system) is set such that it is equal to the number of available electrons in the hydrogen fed into the fuel cell system through the fuel conduit inlet (2 moles of electrons per mole of hydrogen fed per unit of time), subtracted by potential hydrogen losses through leakages. This resembles a fuel utilization of 100 % of the hydrogen fed through the fuel conduit subtracted by potential hydrogen leakages.
• the fuel cell may be a reversible fuel cell, wherein when the fuel cell is operated in an electrolysis mode hydrogen instead of carbon- containing species is produced and hydrogen and optionally water vapour are cycled through the fuel cell. Thereby pure hydrogen can be produced in the same reversible fuel cell system.
• methane can be produced in a highly effective manner, which can be used for other purposes or stored.
• the methanation unit provides water vapour for the electrolysis reaction when methane is produced.
• Fig. 1 a schematic diagram of a fuel cell system according to an embodiment.
• Fig. 1 shows a fuel cell system 1, which is arranged for the conversion of pure hydrogen.
• the fuel cell system comprises one fuel cell 2 comprising an anode 2a, a cathode 2b and an electrolyte 2c provided between the anode 2a and cathode 2b.
• the fuel cell 2 is further arranged for internal reformation in or around the anode (2a).
• Internal reformation means that the conversion of methane, and thus, the reformation reaction of methane, is carried out within the fuel cell 2, i.e. inside the fuel cell and thus, in direct thermal contact with the reaction zone of the fuel cell 2.
• the fuel cell system 1 further comprises a methanation unit 3.
• the methanation unit 3 is configured to produce methane from anode exhaust. Accordingly, an anode outlet 2d and the methanation unit 3 are connected via anode exhaust conduit 4.
• the methanation unit 3 is thermally coupled to a steam cycle 5 and therefore, a third heat exchanger 5a forms part of the methanation unit 3.
• the steam cycle 5 comprises a turbine 5b for generating electric power, which is driven by water vapor. Further provided in the steam cycle 5 are a water condenser or water separator 5c and a pump 5d.
• a fuel conduit 6 connects a fuel conduit inlet 7 with anode inlet 2e.
• a blower 8 is provided and downstream thereof, a first heat exchanger 9 and a second heat exchanger 10 are provided.
• a methanation unit exhaust conduit 11 connects the methanation unit 3 with the fuel conduit 6 upstream the blower 8.
• a water condenser or water separator 12 is provided to separate water from the methanation unit exhaust.
• “Pure hydrogen” means hydrogen with a purity of at least 95 Vol.-% and preferably at least 99.5 Vol.-%, the remainder being unavoidable impurities.
• methanation unit exhaust which mainly contains methane and hydrogen.
• 4 mol of hydrogen per second might be fed through the fuel conduit inlet 7, while the methanation unit exhaust may feed 1 mol hydrogen per second relative to 1.25 mol methane per second to the fuel conduit 6.
• the mixture of 5 mol/s hydrogen and 1.25 mol/s methane is then compressed in blower 8 and reaches the first heat exchanger 9.
• Heat exchanger 9 transfers heat from the methanation unit exhaust to the mixture of fuel including mainly hydrogen and methane, so that the mixture is pre-heated for a first time and the temperature is increased from about environmental temperature (20 °C) to e.g. 300 °C.
• the fuel mixture then enters the second heat exchanger 10.
• heat is transferred from anode exhaust to the mixture so that at the anode inlet 2e, the temperature of the mixture is e.g. about 580 °C.
• Such high temperature is typically necessary for the appropriate operation of Solid Oxide Fuel Cells.
• Anode exhaust leaves the anode outlet 2d at a high temperature of about e.g. 630 °C, this heat being used to further pre-heat the mixture to be supplied to the anode inlet 2e in the second heat exchanger 10.
• the then pre-cooled anode exhaust enters the methanation unit 3 and methane is generated by the exothermic methanation reaction. Since the anode exhaust is entering the methanation unit 3 at lower temperature, the methanation reaction, which is exothermic, is further promoted.
• the methanation reaction produces methane and heat and the heat is transferred to the steam cycle 5.
• the heat can be used to produce water vapor from water and the water vapor can drive a turbine so that extra electric power can be produced and the reaction heat is more effectively used.
• Sensible heat of the methanation exhaust can be used to pre-heat the fuel mixture containing hydrogen and methane in the fuel conduit 6 by using the first heat exchanger 9.
• the temperature of the methanation unit exhaust may then drop to e.g. 80 °C and subsequently water is condensed and separated from the methanation unit exhaust in water condenser or water separator 12. Due to the dependence of saturation pressure and temperature, this leads to a further decrease of the temperature of the methanation unit exhaust to a value ideally close to environmental temperature in order to achieve a low water steam content.
• the water-reduced methanation exhaust is then again mixed with the external hydrogen feed entering the fuel conduit 6 via fuel conduit inlet 7.
• the cathode 2b comprises a cathode inlet 2f and a cathode outlet 2g.
• Oxidant gas like e.g. pure oxygen or air is supplied to the cathode inlet 2g via oxidant conduit 13.
• a blower 14 is arranged as well as a heat exchanger 15.
• the heat exchanger uses heat from the cathode exhaust supplied via a cathode exhaust conduit 16 to pre-heat the oxidant in the oxidant conduit 13, so that thermal energy at the cathode side of the fuel cell 2 is effectively used.
• the fuel cell system 1 is highly efficient. Depending on the operating conditions, such as temperature, pressure, single pass fuel utilization ratio, etc., the fuel cell electrical efficiency is about 70 %, which means that 70% of the heating value of the hydrogen fuel fed through inlet 7 is obtained as electric energy in the fuel cell 2. Additionally, around 10 % electric power can be produced by the steam cycle 5. However, the excellent thermal balance is only achieved since an amount of methane produced in the methanation unit is equal to the amount of methane reformed in the fuel cell so that the content of methane cycling through the fuel cell system is constant. The so-called closed methane cycle is controlled such that the heat produced in the fuel cell 2 is highly consumed by the reformation reaction inside the fuel cell.

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Citations (3)

• 2021
  • 2021-04-29 EP EP21171268.2A patent/EP4084163A1/en active Pending
• 2022
  • 2022-03-02 CN CN202280024846.1A patent/CN117157787A/zh active Pending
  • 2022-03-02 JP JP2023561852A patent/JP2024519270A/ja active Pending
  • 2022-03-02 BR BR112023019681A patent/BR112023019681A2/pt unknown
  • 2022-03-02 US US18/557,581 patent/US20240243318A1/en active Pending
  • 2022-03-02 KR KR1020237041179A patent/KR20240001717A/ko unknown
  • 2022-03-02 MA MA62702A patent/MA62702B1/fr unknown
  • 2022-03-02 MX MX2023012670A patent/MX2023012670A/es unknown
  • 2022-03-02 AU AU2022266955A patent/AU2022266955A1/en active Pending
  • 2022-03-02 IL IL308030A patent/IL308030A/en unknown
  • 2022-03-02 CA CA3211035A patent/CA3211035A1/en active Pending
  • 2022-03-02 WO PCT/EP2022/055295 patent/WO2022228754A1/en active Application Filing
• 2023
  • 2023-10-12 CL CL2023003042A patent/CL2023003042A1/es unknown

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